A total of 2 × 105 K562 cells (program FF-120, solution SF), U2OS cells (program CM-137, solution SE) and CD34+ cells (program CA-137, solution P3) were electroporated on a Lonza Nucleofector 4-D according to manufacturer’s instructions. In K562 cells, 1µg of pX330 plasmid and 0–5 µM (0–100 pmol) ssODN template (Ultramer ®DNA Oligonucleotides from Integrated DNA Technologies) were transfected. InU2OS, 1 µg of pX330 plasmid and 100 pmol of dsODN were transfected for GUIDE-seq analysis. In CD34+ cells, 5 µg (30.5 pmol) of Cas9 protein (Feldan Therapeutics or Integrated DNA Technologies), 2.5 µg (73 pmol) of chemically synthesized gRNAs (TriLink BioTechnologies) and 0–5 µM of ssODN were transfected. For mock-treated CD34+ cells, electroporation of the same amount of cellswas performed using the same P3 buffer and CA-137 program as the treated cells, but without RNP or ssODN.